This invention relates generally to storage tanks of the type designed to contain liquids of different specific gravities and more specifically to a prefabricated modular construction of such tanks in a unique manner to minimize the use of materials, to optimize shipping of uniformly sized parts used in the integrated tank structure and to facilitate on site erection of the novel modular storage tank. The use of prefabricated modular construction to contain large quantities of liquid is generally known; for example, above-ground swimming pools employ this technique. However, the methods used have inherent deficiencies or limitations with respect to the containment of a liquid beyond relative shallow depths, for example, four to five feet. In fact, to contain liquids even at these depths, it has been found necessary to provide laterally extending reinforcing members or struts in conjunction with each vertical frame member. To contain even greater depths would necessarily increase the complexity, expense and weight of these frame members.
The present invention seeks to advance the state of the art in the construction of modular storage tanks for the containment of liquids of various types and at heights of containment of say up to eight feet. The principal object is to produce a tank of modular construction which inherently can be made small or large by the simple inclusion or exclusion of modular units and which is so designed as to greatly minimize the amount of material needed to safely contain large quantities of liquid for commercial purposes. The technique employed adapts certain of the known prior techniques used in the construction of swimming pools in that rigid, vertical and horizontal frame members are employed to reinforce sheet metal panels which in turn contain and reinforce a liquid impervious flexible liner. However, the storage tank of the present invention utilizes frame members designed specifically to withstand the hydrostatic pressure of heights of say six to eight feet and moreover incorporates the use of cross tensioning members to counteract lateral pressure of the contained liquid. Although some forms of containers or enclosures, for example, those illustrated in U.S. Pat. Nos. 1,293,549, 3,382,625 and German Pat. No. 2,048,383, have been known to utilize cross tensioning members for reinforcing, the integration of such tensioning members in conjunction with the other design features of the present invention are believed to be quite unique. It is in fact an aspect of the present invention that the modular tank disclosed herein uses structural material so efficiently that the tank itself would not be permanently freestanding and able to withstand wind loads without the rigidifying effect of the contained liquid. In other words, the structure which is disclosed herein has been designed specifically with the concept of utilizing opposite counteracting forces of hydrostatic pressure and tension. The foregoing aspects will be more completely understood and appreciated upon examination of the specification and drawing which follows: